This application is filed under 35 U.S.C. xc2xa7371 and is based on PCT International Application No. PCT/SE96/01146 which was filed on Sep. 13, 1996.
This invention relates to an industrially applicable process for preparing a fractionated oil from crude vegetable oils, preferably from cereals and grains, the fractionated oil which is obtainable by said process, and to the use of the fractionated oil as a surface active agent in food, cosmetics and pharmaceutical products.
1. Background of the Invention
The production of vegetable oils from various sources, such as soybeans, rapeseed and corn, is based on extraction with as hexane and subsequent refining of the crude extracts to edible oils. The first step in the refining sequence is the so-called degumming, which step serves to separate the phosphatides by the addition of water. The material precipitated by degumming is separated and further processed to mixtures used under the name of lecithins. The commercial lecithins, such as soybean lecithin and sunflower lecithin, are semi-solid or very viscous materials, which consist of a mixture of polar lipids, mainly phospholipids, and oil, mainly triglycerides. These lecithins are by-products from the production of the corresponding vegetable oils and have, after further treatment and purification, found use as surface active materials in many applications, including food, cosmetics and pharmaceutical products.
Wide ranges of conditions for the degumming process are reported in the literature, all of them based on the addition of water, or water solutions, to the crude oils to hydrate the phosphatides and make them insoluble in the oil. Further processing of this crude precipitate, the so called lecithin sludge, involves centrifugation, that is desliming, bleaching by treatment with hydroperoxide and benzoyl peroxide, heat treatment, such as drying or cooking, to give the crude lecithin, which is used as ingredient mainly in food products. The crude lecithin can be further processed in various ways, the most common being purification, such as filtration and adsorption, deoiling, for instance by acetone fractionation to remove the neutral lipids, and fractionation, for instance by means of alcohol treatment to separate alcohol-soluble and alcohol-insoluble components. The established procedure for producing lecithin is shown in Figure.
The methods outlined above are mainly used to produce lecithins from oil crops, such as soybeans, sunflower, rapeseed, corn and cottonseed. In principle all of these are polar lipid rich oils, characterized by being phospholipid rich, particularly phosphatidylcholine rich, consisting of 40-60% oils and 60-40% polar lipids. The content of glycolipids in said lecithins is relatively small, but varies with the source, and the process is designed to give as high a yield as possible of phospholipids at the expense of the glycolipids and other components. Other sources than oil crops, for example cereals, contain more glycolipids than phospholipids.
Glycolipids are well known constituents of plant cell membranes. The most important classes of these contain one to four sugars linked glycosidically to diacylglycerol. The two most abundant classes contain one and two galactose units, respectively, and the commonly used nomenclature and abbreviations of these are mono- and digalactosyldiglyceride, MGDG and DGDG, sometimes referred to as galactolipids. The general structure of digalactosyldiglyceride, DGDG, is outlined below. 
The commercial lecithins, such as lecithins produced from soybean oil, sunflower oil, and rapeseed oil, consist mainly of phospholipids, of which phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are most abundant. PC is the most well characterized class of polar lipids and PC rich materials have found a wide range of industrial applications. Glycolipids have been identified as minor constituents of these lecithins. From an industrial viewpoint it is of a general interest and importance to have access to materials rich in polar lipids other than PC, and also, materials rich in polar lipids other than phospholipids, particularly glycolipids. This relates to the fact that PC and other phospholipid classes are charged, that is contain anionic or zwitterionic functional groups, while the glycolipids are non-charged.
2. Prior Art
There are numerous descriptions in the literature on the use, of lecithins, purified lecithins and phospholipids as surface active ingredients, see for instance xe2x80x9cLecithins: Sources, Manufacture and Usesxe2x80x9d, B. F. Szuhaj, Editor, American Oil Chemists"" society, 1989.
CA 1102795 describes a method of isolating polar lipids from cereal lipids by the addition of at least 50% by weight of water. This method is a modified degumming in the sense that it utilises the principle of adding water to a crude oil mixture.
In Cereal Chem., 1977, vol. 54(4), pp 803-812, lipids were extracted from oat groats by means of diethyl ether and said ether extract evaporated to dryness and reextracted with water saturated n-butanol. After another evaporation the mixture was taken up in chloroform and the lipids obtained were analysed and recorded as bound lipids.
EP 0 290 156 refers to a process for extracting oilseeds by means of a combination of a polar and a non-polar extraction solvent in a counter-current system aiming at a high oil recovery.
Galactolipids, primarily DGDG and DGDG-rich materials have been investigated and found to be surface active material of interest in industrial applications such as food, cosmetics, and pharmaceutical products.
WO 95/20943 describes the use of DGDG-rich material, a xe2x80x9cgalactolipid materialxe2x80x9d, as an emulsifier in oil-in-water emulsions for pharmaceutical, nutritional and cosmetic use. WO 95/20944 describes the use of said xe2x80x9cgalactolipid materialxe2x80x9d as a bilayer-forming material in polar solvents for pharmaceutical, nutritional and cosmetic use; and WO 95/20945 describes the use of the xe2x80x9cgalactolipid materialxe2x80x9d as a lipophilic carrier for pharmaceutical, nutritional and cosmetic use. The DGDG-rich material, the xe2x80x9cgalactolipid materialxe2x80x9d, utilized in said applications was prepared from cereals by extraction of the lipids with ethanol and a subsequent purification on a chromatographic column to pure DGDG or a DGDG-rich fraction of polar lipids. The use of chromatography on a large-scale is expensive compared to the production of, for-example, soybean lecithin by degumming, and there is need for a cheaper way to produce polar lipid rich materials for industrial use, particularly glycolipid rich materials.
The present invention is related to a novel method for producing a fractionated vegetable oil from a plant material.
The present invention provides a novel method for producing purified lecithins or a polar lipid rich fractionated oil, particularly rich in glycolipids, which without further purification can be directly utilized as a surface active agent, for example as an emulsifier in food, cosmetics and pharmaceutical products. The method of the present invention is designed to maintain the concentration of the glycolipids, which implies that the polar lipid rich fractionated vegetable oils obtainable in accordance with the invention are glycolipid rich, particularly digalactosyldiglyceride rich oils. The concentration of the polar lipids can be controlled by process parameters.
In the novel, industrially applicable method of the invention, for producing a polar lipid rich fractionated vegetable oil, a plant material is extracted with a non-polar solvent, and the solvent is evaporated giving a crude oil comprising non-polar and polar lipids, which crude oil is further purified. The method of the invention is characterized in that the crude oil is mixed with an alcohol at a controlled temperature, the alcoholic phase is separated and evaporated and a polar lipid rich fractionated vegetable oil is obtained.
The method of the invention can be described by the following steps:
(a) extraction of a plant material with a non-polar solvent and evaporation of the solvent to obtain a crude oil comprising non-polar and polar lipids,
(b) obtaining a two-phase system by mixing the crude extract with an alcohol, and
(c) obtaining a polar lipid rich fraction by collecting the alcoholic phase and evaporating the alcohol.
The invention is of particular industrial importance for the production of glycolipid rich fractionated oils from cereals and grains, especially oats.
Non-polar solvents are generally water-immiscible solvents, such as saturated or non-saturated, branched or linear alkanes. A preferred non-polar solvent is hexane of industrial grade.
Preferred alcohols to be used in the method of the invention for mixing with the crude oil are aliphatic alcohols having 1-8 carbon atoms, preferably 1-4 carbon atoms, for example methanol, ethanol, propanol and isopropanol.
The alcohol can be used as such or in admixture with water or other polar solvents. In a preferred method the alcohol is used in admixture with up to 35% by weight water, preferably 2.5-20% water.
In the method of the invention the crude oil is preferably mixed with at least equal volumes of alcohol at elevated temperatures.
In a preferred method of the invention the crude vegetable oil is obtained by extraction of oat kernels with industrial hexane. After removal of the solvent the crude extract is mixed with 2 volumes of ethanol (93% by weight in water) at 50xc2x0 C. The upper ethanol-phase is separated from the lower oil-phase at 35xc2x0 C. and the ethanol is evaporated. The remaining oily liquid is the fractionated oil, comprising 40% by weight of polar lipids (of which 79% is glycolipids) and 60% by weight of non-polar lipids, which is used as an emulsifier (1-5% by weight) in a oil-in-water emulsion of evening primrose oil (5-40% by weight) in water.
The method of alcohol treatment included in the invention must be clearly distinguished from the well-known industrial treatment of various lecithins with alcohol (cf. xe2x80x9cLecithins: Sources, Manufacture and Usesxe2x80x9d, B. F. Szuhaj, Editor, American Oil Chemists, Society, 1989; Chapter Seven: Fractionation and Purification of Lecithin). The purpose of such a process is to fractionate the lecithins in alcohol-soluble and non-alcohol-soluble components, consisting mainly of PC (alcohol-soluble) and PE (non-alcohol-soluble), respectively. The method of the present invention does not require any degumming step, which is a major advantage, and can furthermore surprisingly be performed, by appropriate adjustment of the proportions of alcohol to the crude oil and the temperature, to give a predicted concentration of the amount of polar lipids, and thus glycolipids, in the fractionated oil.
A fractionated vegetable oil which has been obtained by the method of the invention is characterized in containing 10-90% by weight of polar lipids, preferably 20-75%, and a remainder of non-polar lipids.
A fractionated vegetable oil which has been obtained by a method of the invention is preferably also characterized in containing more than 5% by weight, preferably more than 20%, glycolipids. Said fractionated vegetable oil also preferably contains more than 3% by weight, preferably more than 15%, DGDG.
The invention further relates to the use of this fractionated vegetable oil without further purification, as a surface active agent for preparing oil-in-water emulsions, water-in-oil emulsions and similar dispersions, reverse vesicles, microemulsions and other organised solutions.
The fractionated vegetable oil obtained by a method according to the invention can also be used as a surface active agent for the formulation of a food, pharmaceutical, skin care or other product for oral, enteral, parenteral, topical or any other form of administration.
The fatty material of these emulsions, other systems and organised solutions can be vegetable oils of all types, such as oils from the seeds and beans of soybean, sunflower, rapeseed (canola), palm, corn, safflower, evening primrose, borage, groundnut, sesame, and similar, furthermore animal oils and fats such as fish oils, liver oils, egg oils, and similar, further-more glycerides, fatty acids, esters and other substances, obvious to a person skilled in the art, which can be emulsified using the fractionated oil.
Preferred oils to be emulsified are selected from a triacylglycerol oil, preferably evening primrose oil or fractions thereof, borage oil or fractions thereof, or other vegetable oils or fractions thereof.
The fractionated oil of the invention, prepared according to the preferred process, consists of a wide range of polar and amphiphilic lipids in a continuous triglyceride phase. It has a low viscosity and a clear appearance. This makes the fractionated oil extremely easy to use as an emulsifier: the fractionated oil is simply added to the oil to be emulsified and the mixture is then gently mixedxe2x80x94no time is needed for swelling of the emulsifier in the oil phase as is the case for conventional, solid or amorphous lecithins.
The highly lipophilic properties of the fractionated oil of the invention are also beneficial from a practical point of view: no atmospheric water and oxygen are taken up during storage which may cause chemical degradation. Furthermore, due to its low viscosity the fractionated oil is easily pumped and thus easily dosed when used in large-scale production of emulsions.
Oil-in-water emulsions are prepared by using the fractionated oil either as the sole emulsifier or in combination with other amphiphilic compounds, as co-surfactants. The oil-in-water emulsion may also comprise optional additives known in the art for improving different aspects of the composition, such as flavouring agents, sweeteners, colorants, thickening agents, preservatives, antioxidants, etc.
Oil-in-water emulsions are prepared by conventional methods. For example, a 30 wt % emulsion of a triacylglycerol oil in water is prepared by adding the emulsifier, that is the fractionated oil, to the oil. The oil phase may also contain oil-soluble additives such as antioxidants and flavours. The total emulsifier concentration is 4 wt %. The oil phase is then gently mixed. The continuous phase may be pure water or an aqueous solution containing water-soluble additives such as sugar, flavours, and preservatives. If necessary, the pH of the aqueous phase is then adjusted. The oil phase as well as the aqueous phase are preheated and then the oil phase is added to the aqueous phase under high-shear mixing. The pre-emulsion is then subjected to high-pressure homogenisation.
The ratio between fractionated oil and oily material in an oil-in-water emulsion could preferably be within-the range of 1:20-1:1 by weight, especially 1:10-1:3 by weight. The total content of oily material in the oil-in-water emulsion is less than 50 wt%, preferably less than 30 wt %.
In addition, the emulsification capacity of the fractionated oil of the invention is surprisingly high; the amount needed for making a 40 wt % oil-in-water emulsion based on evening primrose oil may be as low as 3 wt %, corresponding to approximately 1.3 wt % polar lipids. As a comparison, WO 95/20943 discloses a way of using a polar lipid fraction in an amount of 2 wt % for emulsifying the same type of emulsion.
Conventional fat emulsions based on soybean or egg phospholipids and triglyceride oils may require 1.2 wt % emulsifier for 20 wt % oil-in-water emulsion.
At higher contents of oily material it is possible to obtain oil continuous systems, i.e. systems in which droplets of pure water or aqueous solution are dispersed in the oil phase by means of the fractionated oil. Depending on, inter alia, the content of fractionated oil, the weight ratio between oil and water and the water content, the following organised solutions may be obtained (with decreasing water content): water-in-oil emulsion, reverse micelles (known as an L2 phase or a microemulsion), and reverse vesicles.
The invention also comprises any food, nutritional, pharmaceutical, dermatological, cosmetic or other composition, involving emulsions, microemulsions, reverse vesicles or other forms of preparations, which utilises in its preparation the fractionated vegetable oil prepared according to the invention.
Another advantage of the present invention is its pleasant taste which makes it suitable for use in enteral emulsions.
These oil-rich systems are particularly useful in topical skin care preparations, both medicinal topical skin care preparations and cosmetological preparations. As exemplary topical skin care preparations may be mentioned various ointments containing one or,more active ingredients.
The fractionated oil can also be used as such in practical applications, or mixed with an oil, without adding water or an aqueous solution. As an example, a mixture of 3 wt % salicylic acid in a blend of fractionated oil and a triglyceride oil, such as peanut oil, may be used as a medicinal preparation for treating psoriasis of the scalp.
A preferred pharmaceutical or nutritional composition comprises xcex3-linolenic acid, GLA, or other fatty acids, in the form of a free acid, its salts or esters as emulsified oil. Said pharmaceutical composition can in addition comprise another therapeutically active substance.